Field
The present invention relates to operation control of a fuel cell.
Related Art
A technology has been proposed by which in order to improve stability during startup of a fuel cell in a low-temperature environment such as below the ice point, the waste heat is increased by operating the fuel cell at a lower efficiency than during normal operation, and the fuel cell is heated up in a short period of time. In the fuel cell system according to JP2010-186599A, the volume of the remaining water in the fuel cell is determined based on the impedance of the fuel cell measured during startup or the amount of scavenging air, and if the volume of the remaining water is high and the temperature of the fuel cell during startup is low, the low-efficiency operation is performed while stopping the circulation of the cooling medium inside the fuel cell.
However, the inventors of the application find out a new problem in that if the voltage value of the target operation points of the fuel cell during low efficiency operation is high, the amount of water that is generated until the fuel cell heats up and exceed the ice point becomes large, and the waste heat becomes less, because of which the generated water freezes and the diffusion of reaction gas inside the fuel cell declines, resulting in a significant decline in the output stability of the fuel cell. Moreover, when the present temperature of the fuel cell is the same, but the startup temperature is below the ice point and thus at a relatively low value, the problem of re-freezing also occurs.